Spring Potential Flood Outlook For Northern & Eastern Maine

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE CARIBOU ME
1255 AM EDT Fri Apr 3 2020

...SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN... CENTRAL...AND
DOWNEAST MAINE...

This is the seventh Winter/Spring Flood Potential Outlook for
2020, issued by the National Weather Service in Caribou, Maine.
This outlook is for Northern, Central, and Downeast Maine for the
two-week period of April 2nd through April 16th, 2020.

The flood potential for open water flooding and flooding due to
ice jams, remains near normal for this time of year, with the
exception of Northern Maine, where the flood potential remains
slightly above normal.

...CLIMATOLOGICAL GUIDANCE...

A few storm systems affected the region over the last two weeks
bringing measurable snow and rain to the region. The first
system came in on the 23rd and 24th delivering anywhere from 2 to
9 inches of snow across the region with the highest amounts
from the Maine Central Highlands down to eastern Washington
County. Another system came across the region on the 29th and 30th
bringing more snow changing over rain. This storm delivered
anywhere from 2 to 7 inches of snow across the region. This was
an interesting event as the highest totals occurred across the
Allagash and St. John Valley, with another area of close to 6
inches recorded across the Maine Central Highlands. This event
helped to restore the snowpack across Northern and Northwest
Maine. The warmer temperatures helped to reduce the snowpack
substantially across the Maine Central Highlands down to the
Interior Downeast region, with the Bangor and Downeast region
losing just about all their snow, except for some spots in the
wooded areas.

Temperatures over the last two weeks continued to average above
normal with the stronger March sun, helping to erode the snowpack
and ice on the rivers. Bangor recorded a high temperature of 56
degrees on the 20th, while Millinocket came in with 51 degrees on
the 28th. Temperatures across Northern Maine hit the mid to upper
40s with a few sites back across the Allagash region getting near
50 degrees on the 29th. Over the last two weeks, there were a few
mornings, where temperatures dropped into the single numbers
across Northern Maine wih a few sites dropping below zero.
Caribou recorded a low temperature of -6 degrees on the morning of
the 23rd. This tied the previous record of -6 set back in 2008.
Frenchville recorded a low temperature of 0 degrees on the morning
of the 23rd. Some sites back across the Allagash region reached
close to -15 degrees.

The weather pattern over the next 5 to 10 days will start out
rather tranquil over the next 5 days with a cold front possibly
brining some rain to the region by early Monday. The pattern could
become more active by the end of next week as a storm system
could bring a good dose of precipitation to the region. Some of
the model guidance shows the potential for snow or a mix of snow
and rain. There is low confidence with this system as there is a
large spread in the guidance as to where this system will track
as it moves towards the region.

The official National Weather Service 6 to 14 day outlook is
calling for near to slightly above normal temperatures and near
normal precipitation.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...

As of 7 AM Thursday morning, snow depths ranged from 23 to 40
inches across Northern and Northwest Maine, with Allagash
reporting 39 inches of snow on the ground. The NWS office in
Caribou reported 23 inches of snow depth. Snow depths across the
Maine Central Highlands decreased with the milder temperatures.
Snow depths in this region ranged from 3 to 10 inches with a few
sites reporting up to a foot of snow still on the ground. Snow
depths across the Bangor area and Interior Downeast region ranged
from a trace to 1 inch, with most of this being in wooded areas.
The coastal areas had no snow.

Snow depths across Northern Maine averaged near to slightly above
normal for the 1st week of April, while across the Maine Central
Highlands, snow depths remained near normal. From Bangor to the
coast, snow depths continued to be below normal.

The snow water equivalent, or the amount of water contained in
the snowpack, remained fairly steady over the last two weeks
across Northern and Northwest Maine with 8 to 12 inches of water
in the snowpack. Across the Maine Central Highlands, snow water
equivalents dropped back to 3 to 6 inches with a decrease in the
snow depth. The snow water equivalent from Bangor to the coast was
a trace or less.

Snow water equivalent is above normal across Northern and
Northwest Maine. Across the Maine Central Highlands, water
equivalents remain near normal. Water equivalents from Bangor to
the coast are below normal.

...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...

Soil moisture continues to be near normal for the entire region,
with the exception for Northwest Maine, where soil moisture was
above normal. The latest Palmer Drought Severity Index, which
measures soil moisture in the longer term, continues to show near
normal conditions.

A look at the groundwater levels, courtesy of the USGS, shows levels
are near normal across the region. The latest rainfall helped to
recharge the groundwater levels across the Downeast region.

...RIVER AND ICE CONDITIONS...

River flows are near normal across the entire region. The latest
rainfall has contributed to a recharge in stream flows across the
Downeast region from two weeks ago, especially for the St. Croix
River basin.

As of 7 AM this morning, ice covers about 90% of the rivers and
streams across Northern and Northwest Maine. There has been an
increase in open water on the St. John, Aroostook and Allagash
Rivers. There were open stretches of water from Madawaska to
Grand Isle, and near the International Bridge in Fort Kent.
Otherwise, the river was iced over from west of Fort Kent to
Dickey. The Aroostook River was open in Ashland and had sections
of open water near Presque and Caribou. Ice was still locked in
near Masardis and from Washburn to Crouseville. The ice was
showing signs of thinning. Ice was still in place east of Caribou
to Fort Fairfield with an ice jam in place just west of the Fort
Fairfield bridge. This jam is a mile long. The Piscataquis and
Penobscot Rivers had ice on them with about 50% ice coverage.
There are open sections of water on the Penobscot River from
Bangor up to Millinocket, and along the Piscataquis River from
Guilford to Medford. The ice was thinning and showing signs of
rotting. Across the Downeast region which includes the St. Croix
River, many of the streams and rivers had mostly open water, with
some ice remaining in spots.

Ice thicknesses ranged from 18 to 24 inches along the Aroostook
River with the thickest ice noted near Fort Fairfield. Ice
thicknesses on the St. John and Allagash River ranged from 20 to
25 inches. Ice thickness on the St. John River at Nine Mile Bridge
remains near 25 inches, while the Big Black River in Northwest
Maine, has an ice thickness close to 30 inches. Ice thicknesses
along the Piscataquis and Penobscot Rivers, are 6 to 9 inches. The
exception to this was along the East Branch of the Penobscot
River at Grindstone, where the ice thickness remains at 15
inches. The Kingsbury Stream at Abbot in Piscataquis County still
had some ice, but it was showing signs of thinning and rotting. A
good stretch of the Kingsbury Stream had open water.

Ice coverage and thicknesses remain near normal across the entire
region.

...IN CONCLUSION...

Based on the above information, the flood potential for open water
and ice jam flooding remains near normal, with the exception of
Northern Maine, as the flood potential is now slightly above
normal.

As always, it is important to remember that a heavy rainfall
event along with mild temperatures can lead to an increased
potential for flooding with snowmelt and runoff. Ice breaking up
and jamming can elevate the threat for flooding in a short period
of time.

The next Winter/Spring Flood Outlook will be issued by 8 AM
Friday, April 17th.

$$

Hewitt